Continuum-state and bound-stateβ−-decay rates of the neutron

Abstract

We analyse the continuum-state and bound-state β − -decay rates of the neutron. For the calculation of theoretical values of the decay rates we use the new value for the axial coupling constant gA = 1.2750(9), obtained recently by H. Abele (Progr. Part. Nucl. Phys., 60, 1 (2008)) from the fit of the experimental data on the neutron spin-electron correlation coefficient of the electron energy spectrum of the continuum-state β − -decay of the neutron. We take into account the contribution of radiative corrections and the scalar and tensor weak couplings. We define correlation coefficients of the electron energy spectrum in terms of axial, scalar and tensor coupling constants. Using recent precise experimental data for the lifetime of the neutron and correlation coefficients we estimate the scalar and tensor weak coupling constants. The bound-state β − -decay rates of the neutron we calculate as functions of axial, scalar and tensor weak coupling constants. We show that dominantly the neutron decays into hydrogen in the hyperfine states with total angular momentum F = 0. The calculated angular distributions of the probabilities of the bound-state β − -decays of the polarised neutron can be used for the experimental measurements of the bound-state β − -decays into the hyperfine states with a total angular momentum F = 1. PACS: 12.15.Ff, 13.15.+g, 23.40.Bw, 26.65.+t

Neutron lifetime from a new evaluation of ultracold neutron storage experiments

“…Fig. 13 shows this analysis which is discussed in detail in [28,29]. Fermi transitions only [30,31].…”

Neutronβ−decay as a laboratory for testing the standard model

“…(6) over the directions of the electron 3-momentum k e , the antineutrino 3-momentum k and the electron energy E e within the limits m e ≤ E e ≤ E 0 , we obtain the rate of the neutron β − -decay. It is equal to [10] (…”

“…It is well-known [1,2] that in the non-relativistic approximation to leading order in the large proton mass expansion, which is equivalent to the leading order of the heavy-baryon approximation, and in the rest frame of the neutron the SM with weak V − A interactions [9] describes the β − -decay of the neutron in terms of two coupling constants G V and G A [1,2] (see also [10]). The coupling constant G V is defined by the product G V = G F V ud of the Fermi coupling constant…”

“…The lifetime of the neutron and the correlation coefficients under consideration are of order τ n ∼ 880 s, a 0 ∼ a(E e ) ∼ A 0 ∼ A(E e ) ∼ −0.1 and B 0 ∼ B(E e ) ∼ 1 [9]. The coupling constants G V and λ define the main contributions to the lifetime of the neutron and the correlation coefficients [1,2] (see also [10]). …”

“…Indeed, it is well-known that the radiative corrections to the lifetime of the neutron [13]- [30], calculated to leading order in the large proton mass expansion within the SM with the V −A weak interactions and Quantum Electrodynamics (QED), give the contribution of about 3.9 % [28] (see also [1]). This allows to describe correctly the lifetime of the neutron [10]. The radiative corrections are very important also for the correct determination of the Fermi coupling constant G F .…”